Susan Slattery and her two sons, Matthew and Peter, were on their way home from visiting family in Ohio on a sunny August day in 2010 when tragedy struck. A truck driver fell asleep at the wheel, barreling into Susan Slattery’s car and pushing it under a tractor trailer, killing her and critically injuring 12-year-old Matthew and 16-year-old Peter. Peter fractured his pelvis and eye socket, while Matthew suffered a severe traumatic brain injury, losing 80 percent of his blood.

Tell a kid to do three repetitions of 15 pushups or 25 leg lifts or any of the other myriad exercises that physical therapists assign during a regular session, and the automatic response might be a roll of the eyes and a groan before relenting—only to tucker out and lose focus or motivation before it’s over.

What happened next would change Ben’s life forever, and no one could possibly have seen it coming.

It was a perfect day at the beach. The sun was shining, and the water was just right. Ben and his friends splashed in the waves and built sand castles, while his mom Joanne and the other parents chatted under the umbrellas, keeping a watchful eye on the children. But as the day came to a close, everyone headed back to the house, just a few blocks away.